The field of the invention is that of interactive services in a telecommunications network.
Although this is not limiting on the invention, the field of the invention is more particularly that of interactive multimode services.
The term “multimode” refers generally to alternating or parallel use of a plurality of modes in a combined or redundant way.
From the system point of view, an input or output mode is defined by:                a representational system;        a physical interaction device; or        a representational system and a physical interaction device in association.        
By way of non-limiting example, the invention applies to interactive services accessible in one or more of the following modes:                fixed telephone;        mobile telephone;        Internet Protocol (IP) telephone;        Internet access;        video.        
A user (a physical person or a device) accesses a service during a session that is linked to that user and during which one or more channels are set up.
A session set up between two entities is controlled (set up, maintained, released, etc.) by control means distributed between those entities.
In the present document, data managed by at least part of these session control means is referred to as data “attached” to the session.
A communications channel between two entities is defined by a payload data stream (voice, video, etc.), means for controlling this stream being distributed between the two entities. The data managed by these channel control means is referred to as data “attached” to the channel.
Data attached to a first session or a first channel is said to be “visible” from a second session or from a second channel if the control means of that second session or that second channel are aware of the existence of the data. Otherwise the data is referred to as “invisible”.
Finally, if data is visible, it can be visible:                in “read” mode, if its value can only be obtained; or        in “read/write” mode, if its value can also be modified.        
Moreover, and notably in the context of multimode services, one or more users can access the same service with a number of sessions, each including one or more channels.
For example, a user might access a server via a voice channel of a first session set up between that server and a mobile telephone of that user and simultaneously via a video channel of a second session with a computer of the same user.
At present, the deployment of multimode services remains limited because it is not possible in the current state of the art to share information between the various channels, this relative impermeability effect preventing overall service consistency.